1. Field of the Invention
The present invention pertains to actuators. More specifically, the present invention pertains to actuators for converting linear motion to rotary motion. Still more specifically, the present invention pertains to a linear to rotary motion actuator suitable for use with a rotating type valve.
2. Brief Description of the Prior Art
There are many types of actuators suitable for converting linear motion to rotary motion. Several of these actuators are suitable for operating a rotating type valve. Such actuators may be operated manually, hydraulically, electrically, etc.
One type of widely used valve actuator is the diaphragm type which employs a diaphragm member mounted in the actuator housing for movement, in response to pressure applied to one side thereof, between first and second terminal positions. The actuator is also provided with biasing means for biasing the diaphragm member toward one of its terminal positions. A rod member is connected to the diaphragm member for reciprocal movement between first and second terminal positions in response to the travel of the diaphragm member between its terminal positions. The opposite end of the rod member is connected to a crank member which is in turn connected to the operating shaft of the valve to be operated by the actuator. The crank member is rotatable, about the axis of the valve operating shaft, in response to reciprocal movement of the rod member to open and close the valves.
Such operators are commonly designed for 90.degree. rotation of the valve operating shaft since many valves move from a completely closed position to a completely open position with 90.degree. rotation. However, it is not uncommon for some rotation of less than 90.degree., say 60.degree., to be required, for example, in installations requiring throttling control. In the past, converting a 90.degree. rotating actuator to one of something less has required the replacement of one or more of the actuator components, for example, the crank member. This requires that alternate parts be manufactured and kept in inventory for such changes.
In addition, the biasing member of such actuators, usually coil springs, occasionally need adjustment to increase or decrease the tension exerted thereby. In the past, such adjustments have required disassembly of at least a portion of the actuator. This is of course time consuming and may require that the valve to which the actuator is connected be placed out of service.
Furthermore, such an actuator is usually installed to close or open the valve to which it is connected, depending upon the particular service, when the pressure source to which it is connected fails for some reason. Thus, the actuator may be said to be installed for "fail-open" or "fail-closed" action. To convert an actuator from a fail-open operation to fail-closed operation may require the replacement of various components or it may require an additional means of engagement of the crank member with the operating shaft of the valve member.
In short, the versatility of the valve operators of the prior art leave something to be desired. Furthermore, to achieve such versatility extra parts must be manufactured and kept in stock for the customer, resulting in increased manufacturing and storage costs not to mention the inconvenience of having to order replacement parts and to replace the original components therewith.